Bed rest flat on a firm mattress or with a board under the mattress to keep the spine straight and minimal weight on it.
OTC (over the counter) meds such as the non-opioid pain relievers bought without a doctor’s prescription. See drug treatment.
Exercises to theoretically strengthen the spine muscles and reduce strain on the disc. However, these exercises often place weight on the spine, which can keep the disc from receding or even make it worse. Two schools are in vogue; the “Williams” flexion exercises (lie on the back and raise shoulders and legs) and the opposite, extension exercises (lie on stomach and raise shoulders and legs). Be careful with sit-ups, as they definitely increase the pressure inside the lumbar discs. After having two micro-lumbar disc operations myself, my preferred lower back exercise is the plank, where you raise your abdomen off the floor and rest on your toes and elbows, keeping the spine straight. Hold that position as long as you can, rest and repeat once or twice and do at least three times a week.
Back Braces of various types to support the lower spine. They probably help some by pushing in on the abdominal cavity and forcing pressure up and down along the spine, like squeezing a balloon. Braces also reduce movement on the spine, which may reduce pain.
Auto-traction devices can be as easy as hanging from a high bar, either by the knees or the hands, to complicated devices with pulleys or tilt tables to put a pulling force along the spine. Hanging upside down has some risk of causing a detached retina.